THE GRANITES
GOLDMINE
North Flinders Mines Limited
(Incorporated In &A)
GOLD ROOM
OPERATIONS MANUAL
Produced By
Michael Hand
(Senior Foreman)
ACKKOVLEPGEMBITTS
The development of the Intensive Cyanidation Procedure
involved considerable test work. For the initial
feasibiltiy studies much is owed to Ian McGrattln,
consultant metallurgist. The first full scale batch
treatments were conducted by Ron Wilson, gold room
foreman, in consultation with Keith Goble-Garrett ,
plant metallurgist. These trial treatments resulted in
the setting down of operational procedures as detailed
by Ron in section 6.4c of this manual.
The comprehensive coverage of the Vilfley table, Part
5.3, was written by Ron Wilson.
Rachel Chisholm very kindly prepared the cover for
this manual.
M.H.
CONTENTS
Page
Acknowledgements.
List of Figures.
Introduction.
PART I - THE STRIPPING SYSTEM.
1 . 1 General .
1.2 Sequence Controllers.
1.3 Description of Stripping Process.
1.4 Electrowinning.
1.5 Operation of the Stripping System.
1.6 Fault Finding Procedure for the Stripping System,
PART 2 - THE SEQUENCE CONTROLLERS,
2.1 Acid Vash and Rinse Steps.
2.2 Acid Vash and Rinse Instructions and
Output Settings,
2.3 Stripping Sequence Steps.
2.4 Stripping Sequence Instructions and
Output Settings.
PART 3 - OPERATION OF THE STRIPPING SYSTEM .
(Step by Step Procedure)
3. 1 General .
3.2 Acid Vash.
3.3 Washed Carbon Transfer.
3.4 Reagent Addition and Pre-Treatment,
3.5 Elution.
3.6 Transfer of Barren Carbon to Regeneration
Kiln Hopper.
3.7 Electrowinning.
3.8 Stripping System - Optimization of
Reagent Usage.
PART 4 - THE STRIPPING SYSTEM - FAULT FINDING.
4. 1 Acid Vash.
4.2 Transfer of Loaded Carbon to Elution Column.
4.3 Reagent Addition and Pretreatment Stage.
4.4 Elution and Carbon Cool.
4.5 Transfer of Barren Carbon to Regeneration.
Kiln Hopper.
PART 5 - THE GRAVITY CIRCUIT.
i
(iv)
(v)
5. 1 General.
5.2 The Spirals,
a. Optimum Operating Conditions.
The Static Distributor.
1
2
3
5
5
5
8
9
10
11
b.
c
d.
e.
The Primary Spiral.
The Cleaner Spiral.
Maintenance of the Spirals.
12
12
13
13
15
15
17
19
2
2
2
2:
2
2
2
2
2
2
PART 5
- THE GRAVITY CIRCUIT. (Continued)
5.3 The Vilfley Table.
a. General Description. 28
b . The Head Hot ion . 29
c. Adjustment of Deck. 30
d. Action of Table. 31
e. Operation of Table. 31
f . Maintenance of Vilfley Table. 32
5.4 Starting Up and Shutdown Procedure for
the Gravity Circuit. 33
PART 6 - PREPARING OF GRAVITY CONCENTRATES FOR SMELTING.
6. 1 General. 34
* 6.2 Amalgamation. 34
6.3 Acid Digestion. 34
6.4 Intensive Cyanidation.
a. General, 37
b. Description af Plant. 37
c. Operation of Plant. 38
d. Further Considerations. 40
PART 7 - PREPARING CATHODE VOOL FOR SMELTING.
7 . 1 General . 42
7.3 Removing the Wool. 42
7.3 Acid Digestion of Wool. 42
7.4 Drying the Cake. 43
PART 8 - SMELTING.
8 . 1 The Furnace . 45
8.2 Crucibles Used. 45
8.3 Moulds Used. 46
8.4 Fluxes Used. 46
8.5 Smelting Procedure. 47
8.6 Points to Watch. 48
PART 9 - CARBON REACTIVATION.
9. 1 General. 49
9.2 Start Up Procedure. 51
9.3 L.E.D. Readouts. 51
9.4 Shutting Down the Kiln. 53
9.5 Adjustment of Rate of Carbon Discharge. 53
9.6 Adjustment of Vibrator Intensity. 53
9.7 Points to Watch. 54
PART 10 - GOLD ROOM GENERAL.
10. 1 Other Gold Room Duties. 55
10.2 Security. 55
10.3 Safety. 57
10.4 Reagents - Their Effects on Human Beings,
, First Aid Requirements, Handling and Disposal. 59
REFERENCES 68
Civ)
LIST OF FIGURES
fc.-. »
Fig.
1.
2.
3/
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14,
15.
16.
17.
18,
19.
20.
Flow Diagram of the Stripping System.
Control Panel for the Stripping System.
Carbon Fill Selector ,
Mill/Gravity Circuit Flow Diagram.
The Gravity Splitter Box.
The Static Distributor.
The Spiral Discharge Splitters.
The Vilfley Table.
The Vilfley Table Head Motion.
The Vilfley Table Stroke Pattern.
The Vilfley Table Rocker Pockets.
The Vilfley Table Tilting Mechanism.
The Vilfley Table - Inverse Classification
and Stratification,
The Vilfley Table - Lines of Separation.
The Vilfley Table - Concentrate Launder
and Splitter.
The Intensive Cyanidation Pilot Plant.
The Decant Platform.
The Barring Furnace,
The Carbon React! vat i on Kiln.
The Carbon Reactivation Kiln Control Panel.
Page
4
6
12
24
25
26
27*
28
29
29
30
30
31
32
32
36
42
45
50
52
i
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(V) i
INTRODUCTION
was
to
The Carbon- in-Pulp technique as practiced at The Granites
initially introduced into the gold processing industry so as
by-pass the counter current decantation and filtration steps o±
the Merril-Crowe cyanidat ion-zinc cementation procedure.
Early development was hampered by a lack of suitable carbon
offering good activity, mechanical strength and satisfactory
price.
With the gold price rise of the seventies, the C.I. P. process
has developed rapidly and there has been a rapid growth in the
number of C.I. P. plants along with an equally rapid growth in
technology and innovations in plant practice.
It is now generally accepted that the C.I. P. procedure offers
substantial savings in both capital and operating costs over the
Merril-Crowe procedure at low head grades (<15g Au/tonne). The
C.I. P. procedure has in fact made ore reserves with head grades
of <5g Au/tonne commercially viable and many of the more recent
developments are based on such reserves.
At The Granites head grades of >10g Au/tonne are commonplace and
the nature of the feed is such that this plant would be
hard-pressed to achieve good recovery, without a substantial
drop in the rate of production, but for the improved efficiency
of the gravity circuit.
It has been possible to reduce the number of strips each week
and this has led to substantial savings in the use of reagents,
gas and potable water ,
Success in the production of gravity concentrates has prompted
investigation into alternative methods of treating concentrates
for smelting so that the present practice of Acid Digestion,
along with its inherent dangers and operator discomforts, may be
dispensed with.
Current experiments with Intensive Cyanidation have met with
considerable success and if problems relating to the subsequent
extraction of gold from the loaded Intensive Cyanidation product
are overcome, this method could well supersede Acid Digestion.
This manual has been compiled in an attempt to familiarize all
gold plant personnel with gold room operations and developments
and in particular, to give C.I. P. plant operators and
maintenance personnel, a better understanding of the areas of
gold room operations in which they are directly associated.
FART 1 - THE STRIPPING SYSTEM
1 . 1 General
The Anglo American Research Laboratories (AARL) stripping
system used at The Granites has two definite advantages when
compared with its most common counterpart, the Zadra system.
It is much less expensive to operate and it produces a
cleaner stripped carbon. It is however very reliant upon the
availability of an abundant supply of good quality water and
its water usage is far greater than that of either the Zadra
.system or the mare recently developed solvent stripping
system.
The stripping of gold from loaded carbon here involves two
basic steps; Acid Washing and Elution. The elution step may
be further divided into two major stages; carbon
preheat and elution" proper .
At The Granites a separate column is provided for acid
washing. The advantages of this are dubious in that there
would be more than enough time in a twenty four hour period
for both steps to be completed in one column. In any case the
potable water system here does not cater for the running of
both steps at the same time. Much greater benefit would have
been derived from the provision of an additional eluate tank
as it is in the later electrowinning stage that most of the
present hold ups occur.
a . Acid Washing
This involves the soaking of the loaded carbon in a 3% HCL
solution in order to remove impurities such as ca lcium,
copper and magnesium which can impede both the elution step
and the later adsorption of gold onto the carbon after it has
been returned to the C.I. P. circuit. Acid washing of carbon
is in fact used as a temporary substitute for thermal
reactivation of carbon in some plants.
b. Preheat Stage
During this stage a 2% caustic/3% cyanide solution mixture is
re-circulated through the loaded carbon in the elution column
until such time as a predetermined "top of column'
temperature is reached. By this time most of the gold and
silver on the carbon will have been desorbed into solution
and both the carbon and the solution will have reached an
optimum temperature for the subsequent elution proper.
c . Elution stage
During this stage the gold and silver desorbed off the carbon
during the preheat is washed out of the column into the
eluate tank. This stage takes 2 1/2 hours and involves the
use of 5 bed volumes of potable water <21.6 cubic metres).
The critical factor during this stage is temperature. It has
been found that the optimum "top of column* temperature is
around 110~c
1 . 2 Sequence Controllers
The goldroom uses the Anglo-American Research Laboratories
stripping system to strip gold from loaded carbon in batches
of approximately 1.9 tonnes. The process is fully automated
and controlled by electronic sequence controllers which
switch both pumps and valves for each step.
The controllers can be over-ridden to stop or reset a cycle
or to start again, at any point. It should be remembered that
no feedback to the controllers is provided and hence a signal
for a pump to run or a valve to open does not necessarily
mean that the item is operating. This can be confirmed by
visual inspection at the pump or valve. Likewise it should be
remembered that the control lers will not operate if a local
stop switch is depressed. <See fig. 2 on page 6)
Although the sequence controllers govern
the various stripping stages it is
essent ial to monitor the plant on a
regular basis so as to ensure that all
equipment is operating properly and that
desired temperatures are being reached
and maintained within the time
limitations set on the controllers. Here
goldroom foreman, Ron Wilson, checks the
panel prior to start up.
-3-
li3 TteRcriDtlon nf the Strippin g F rnnnB. (See fig- 11
*' CarbofTs loaded into the acid wash column from the loaded
carbon surge hopper by opening the main inlet valve AV 401^
carbon surge * « * nf f through a screen and valve
Excess water and air are bled off througn a ^ hopper.
AV 414 to either the leach area sump or the failings Copper.
After fillinjr, the main valve AV 401 is closed and dil^
S^rocnior^kcid is injected into the bottom of the column
via valve AV 403 Displaced water "o^*^,^ ho * per .
the column through valve AV 414 to ed B int o the
After acid injection and soaking. wM*r is pu p
bottom of the column via valve AV 404 and as
' through the column to exit via valve AV 414, it rinses
the acid,
b . Transfer to F.luti on Column transferred to the
A f e t i ri roiuL th Wat a e r r b i n s J3JST2E column
line via valve AV 402 and the carbon is forced along tne
iine through valve AV 422 into the elution column. WJf^*
„a"r flowl out of that column ttomgtt. inlin. filter,
via valve AV 415 into the potable water tank.
NaCH <2 to 3%) and Na5S C2*> to the column via valve AV 410^
Displaced water flows out of the top of tl« cOl««
the P inline filter, along the pregn-nt solution line to
heat exchanger to exit via valve AV 410
tank.
jj.4.j~„ »V 416 closes and the elution
After reagent ^dition v a ive AV 416 c by
water pump recirculates tne so-lui-x AV 40 9 up
pumping it via the Xt"S v. « AV 460 back to the
through the f » ^ f ^ h t solution as it
rasres P th P rourh ;he\ert a :xchan e g d er from thermal which is
whlcnhTdJirfd -top of the column' temperature £ould *•
~ + + *i-n<*d Bv this time most of the gold will nave pw«
preheat and subsequent elution stage so as
desired operating temperatures.
d. Elution and Carbon Cool +>1 _ rotable
During the elution cycle, water is drawn from the P°^^
w tlAank and pumped through the heat -changer via valve
AV 409 into the column. The water then flows up £rougn
column, taking with it gold ^ at has ^ f Elution
solution during the preheat stage. This pregnan
then flows out of the column through the inline filter and
the heat exchanger, then via valve AV 416 to
-5-
tank. This stage continues until five bed volumes of water
have passed through the column (2.5 hours) after which
desired barren carbon assays of -30g Au/tonne should be
achieved.
At the end of the elution stage the thermocal heater stops
and an additional amount of KaOH is pumped into the eluate
tank via valve AV 420, this bringing the pH of the eluate
solution up to the desired level. Potable water then
continues to flow through the system as per the elution
stage for another twenty minutes, this taking some of the
heat out of the carbon and the thermocal. The thermocal
pump operates for another two hours after the end of the
carbon cool stage, this aiding the cooling down of the
heater.
e. Transfer of Barren Carbon to the Regeneration Kiln Hopper
At the end of the carbon cool stage, water is pumped into
the column via valve AV 409 so as to maintain pressure
within it and force the barren carbon out of the column via
valve AV 421 into the carbon transfer line. Additional water
is injected into this line via valve AV 412 and the carbon
is carried long the line to the dewatering screen above the
regeneration kiln feed hopper.
1. 4 Electrowinning
One bed volume (thirty minutes) into the elution stage the
eluate pump is started and pregnant solution from the eluate
tank, is pumped up into the electrowinning cell on the first
floor of the goldroom. It then flows back into the eluate
tank. As the solution flows through the electrowinning cell,
gold is plated on to the steel wool cathodes. This
recirculation process continues for around 14 to 16 hours
after which period of time there should be no more than -lg
Au/tonne of eluate remaining in solution. The barren solution
is then pumped out of the eluate tank into the process water
tank.
1 . 5 Operation of the Stripping System
Details of the step by step sequence controller operation for
the entire stripping process are out 1 ined in part 2 . This
information is displayed on the control cubicle. The mere
following of the instructions given in that section will not
ensure effective stripping results as there are many
extraneous factors which need to be taken into account. Part
3 outlines in full detail every action required on the part
of goldroom personnel in order to operate the plant
successfully. Operators unfamiliar with The Granites
stripping system should follow Part 3 directly. Loose copies
are available. "Operation of the Stripping System - Step by.
Step Procedure".
1.6 Fault Finding Procedure for the Stripping System
Should any difficulties occur during the stripping process,
possible faults with remedial action have been detailed in
part 4 of this manual.
Sequence
complete
-6-
CD
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31 1
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Fig, 2 Control Panel for the Stripping Syst
-7-
1 STEP . . . Step display
2 INSTRUCTION , . . Instruction
display, The STEP display
indicates the step number
(or process) in progress,
and the INSTRUCTION
display consisting of OP,
DATA-1 and DATA- 2 displays
indicates the step advance
conditions. These displays
are used for monitoring the
keyboard programming, as
well as monitoring the
program being executed,
3 RUN . . . Run display (LED)
The LED indicator lights
when the START switch is
depressed in the manual or
automat ic mode and goes off
when the STOP switch is
INPUT , . . Input display
(LED) For indication of
input status.
Output operation
CLED) The LED
5 OUT . .
display
Indicator lights when the
output is not prohibited
6 OUTPUT . , . Output display
(LED) For indication of
output status. The LED
indicator also illuminates
when the OUT ON/OUT OFF
selector switch is set in
the "OUT OFF" position.
7 FLAG . . . Flag display (LED)
For indication of flag
status. The LED indicator
also illuminates when the
OUT ON/OUT OFF selector
switch is set in the "OUT
OFF" position.
8 Operation switches:
AUTO/M/E . AUTO se lector
switch
AUTO . . Automatic
operation mode selection.
M . . Manual operation
mode selection
E.AUTO Automatic or
manual mode selection by
external siRnal.
OUT ON/OUT OFF selector
switch . . In the OUT OFF
position, outputs
(including flag outputs)
are prohibited. The OUT
ON position allows
outputs to be generated.
RESET switch . ■
Depressing this switch
causes the program to
reset to step 01 and
places the controller in
STOP state.
START switch
Depressing this switch
places the controller in
RUN state, causing
automatic or manual
operation to start.
STOP switch . . Depressing
this switch places the
controller in STOP state
causing the current step
to be held.
9 Program Console
Keyboard switches for
programming. Program
console switch must be
turned on when programming.
10 Battery Lid
Battery, unit number
setting switch for
parrallel processing and
program protect switch are
mounted in
11 Unit Number Setting Switch.
Sequence Controller Operations
-8-
PART 2 ~ THE SEQUENCE CONTROLLERS
2. 1 Acid Wash and Rinse Steps
Refer
Job Step Action
I, 01 Press SEQUENCE START. "Run" and "Output"
lights show. Manually initiate sequence by
switching the Carbon Fill Selector switch
to "Fill" and then "Complete" after the
column has filled with carbon.
^ 2. 03 Press ACID WASH RINSE START. This adds
concentrated HCL and water to the column.
04 Allows soak in acid.
05 Rinses carbon column with water to remove
acid and restore neutral pH to the
solution
3. On completion of the water rinse step, the
alarm will sound. Press ALARM ACCEPT.
4. 10 Press WASHED CARBON TRANSFER START to
commence the transfer of carbon to the
elution column.
5. On completion of transfer the alarm will
sound. Press ALARM ACCEPT and then shut
down by pressing WASHED CARBON TRANSFER
Note:
Sequence is ended.
CI) During the carbon transfer take LOADED CARBON
samples from the sample point on the transfer line.
<2) Complete log sheet by recording times and volumes of
water used during this sequence.
(3) The programme can be interrupted at any stage by
pressing SEQUENCE STOP. It can be resumed by
pressing SEQUENCE START. The cycle will then start
again from the point at which it was interrrupted.
-9-
2. 2 Acid Wash and Rinse Instructions and Output Settings
INSTRUCTIONS
STEP OP. DATA DATA
NO. 1 2
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03
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OUTPUT SETTINGS
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14
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CODE
ACTIVITY
4 Instructs the programme to proceed to the next step.
9 The programme carries out the instructions shown by the
output setting for the time shown in Data 1 and Data 2.
Times may be varied.
1 This causes the programme to reset to Step 01
2 The programme advances to the next step.
-10-
2. 3 Stripping sequence steps
Fefer
Job Step Action
1* 01 Press SEQUENCE STAFT. The "Run" and
"Output" lights will show on the panel.
2. 02 Press STRIPPING CYCLE START. Cyanide
and caustic are added to the elution
column to soak the bed of carbon,
05 In this cycle the strong cyanide and
caustic solution is circulated. The
temperature is raised from ambient to
90-C.
06 The stripping stage is done by
continuously pumping water at about
110°C through the bed of carbon in the
elution column. The pregnant solution or
eluate, flows into the eluate tank.
07 An addition of caustic is made to the
eluate .
09 The cool rinse stage. The burner shuts
off (The thermocal pump will continue to
run for two hours) and cool water is
pumped through the elution column.
3. On completion of the stripping cycle, the
alarm will sound. Press ALARM ACCEPT.
4. 13 Press STRIPPED CARBON TRANSFER START to
commence transfer of carbon to the
regeneration kiln feed hopper.
5. The alarm will sound at the end of the
designated transfer time. Press ALARM
ACCEPT. The transfer pump will still be
operating. If all of the carbon has been
transferred (check sight glass) stop by
pressing STFIPPED CAFBON TRANSFER
Sequence is ended,
Note
1. During the carbon transfer take STRIPPED CARBON
samples from the sample point on the transfer line,
2. The electrowinning cell may be started after one bed
volume has passed through the column in step 6.
3. Fill in the relevant information on the log sheet.
4. To stop programme at any stage press SEQUENCE STOP
Eesume programme by pressing SEQUENCE START
-11-
2 4 Stripping Sequence Instruc t ions and Output Settings
OUTPUT SETTINGS
r
INSTRUCTIONS
STEP
NO.
00
01
02
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OP. DATA DATA
1 2
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72
71
50
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74
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The programme carries out the instructions shown by the
output setting for the time shown in Data 1 and Data 2.
Times may he varied.
Instructs the programme to proceed to the next step.
This causes the programme to reset to Step 01
The programme advances to the next step.
-12-
PART 3 - OPERATION DF THE STRIPPING SYSTEM
(Step by Step Procedure)
3. 1 General
a. Check the electrowinning cell and take a sample over to the
laboratory. Label the sample:-
"E/V Ko. DATE TIME TAIL"
• b. Check the potable water meter reading and the available
potable water (off tank level indicator); and the gas
pressure. Note these on the log sheet for the preceding
day.
3.2 Acid Vash
a. After ensuring that there is sufficient carbon in the
loaded carbon surge hopper, switch the valve control
switch (See fig. 3) to "auto' to open the valve.
OFF
Fig. 3 Carbon Fill Selector
Then put a running hose in the hopper and wait for the acid
wash column to fill with carbon. When the carbon is visible
in the top sight glass switch the control switch back to
"manual' to close the valve. Check to ensure that the
inline trash screen is clear.
b. Make sure that the manual valve on the acid container is
open. Record the time, the level of acid in the container
and the reading for potable water off the meter by the
potable water tank, on the goldroom log sheet. Press the
"acid wash/rinse start' button on the main control panel.
c. Check to see that the acid pump is running. As soon as it
stops check and note on the log sheet, the acid level in
the container. Also close the manual valve on the
container.
d The sequence control ler wi 1 1 automat ical ly take the
sequence through the soak step (04) and the rinse step
(05). At the end of step 5 the alarm will sound. Check the
pH level of the solution from the sample point at the top
-13-
of the column. If it is over 5 press the "alarm accept'
button.
3. 3 Vashed Carbon Transfer
a Press the "washed carbon transfer start* button on the
control panel. Whilst the carbon is being transferred take
samples from the transfer line sample point, every five
minutes. Rinse the combined sample and label it:-
"STRIP No. DATE LOADED Au content"
b. Towards the end of the carbon transfer step the alarm will
sound. Press the * alarm accept* button but do Not press
the "washed carbon transfer stop' button until the acid
wash column is seen to be empty by way of both the bottom
of column sight glass and the absence of carbon in the
transfer water at the sample point.
c. After the transfer is completed and you have pressed the
"washed carbon transfer stop* button, drain out the
accumulator vessels by way of the two ball valves near the
right hand side vessel and then clean out the filter bag at
the top of the elution column. Hake sure that the filter
bag has no holes in it and that the pliable band fits
snugly into the ledge inside the filter housing. Also
ensure that the steel ball has been put back inside the
bag,
d. Close the accumulator drain valves and also the manual
up valve on the barren carbon transfer line.
-
3.4 Reagent Addition and Preheat
a. On the log sheet, note the meter readings for the caustic,
and cyanide pumps and also that of the potable water
supply.
b. On the elution control panel press the "sequence start*
button and then the "stripping cycle start' button. This
step will not commence if the eluate tank 'low level' light
is not on. i.e. the tank has not been pumped out or the low
level indicator is faulty.
c. During the addition of reagents step (02) visually check
that the pumps are operating and also record the meter
readings immediately after the pumps stop. Should the
output of either pump be drastically short of the desired
amount (Presently 565 litres of cyanide and 100 litres of
caustic) immediately press one of the pump stop switches
and then reset it, This action will prevent the sequence
controller from continuing on through the elution
programme. It will then be necessary to add additional
reagent by the steps outlined below; -
Ci) Switch the controller to "manual' by way of the
black selector switch on the main control panel
(ii) Open auto valves AV 410 and AV 416 manually.
(ill) Start the desired reagent pump locally and run it
until the desired additional litres have been added
as per meter.
Civ) Reset the pump stop switch.
(v) Close auto valves AV 410 and AV 416 manually.
<vi) Switch the controller back to "auto* .
<vii ) Press the "sequence start' button on the control
panel. The controller will automatically continue
on with the preheat cycle (step 05) .
d. Check to ensure that the thermocal heater is operating. If
it fails to start it is most likely to be because the
thermocal pressure is too low as a^result of an airlock in
the heater circuit. Correct this by opening the ball valve
above the "thermocal in* line for thirty seconds or so. If
some time has elapsed before it was noticed that the heater
was not going, the preheat step (05) should be restarted by
the following method: -
(i) On the sequence control panel, switch the left
hand side toggle switch from "auto* to "m' and the
adjacent toggle switch from "out' to "out off .
(ii) Press the white "reset* button next to the toggle
switches.
(iii) By pressing the blue "start* button step the
controller through to step 05 again.
(iv) Put the toggle switches back to "auto* and "out on'
respectively. The preheat step will then
automatically commence again and run for the full
set time.
e. Monitor the preheat step regularly and record both
temperatures and pressures on the log sheet every half
hour, the desired top of column temperature at the end of
the preheat step varies with weather conditions, but
during the cooler months it should reach 90^
approximately. If this temperature is not reached then the
preheat step will need to be extended by switching the left
hand side toggle switch to "m* . The preheat step will then
over-ride the timer and continue on until the toggle switch
is put back to auto.
-15-
f, Should the column pressure rise rapidly during preheat to
above 400 kPa, it may be necessary to stop the cycle.
Either stop the elution pump locally or press the red
"sequence stop' button on the control panel. Then drain
the accumulator vessels until the top of coulumn pressure
falls below 150 kPa. Restart by resetting the pump stop
switch and pressing the "sequence start' button on the
control panel.
3 . 5 Elution
a. After preheat the controller will automatically go into the
elution step (06). Monitor this step regularly and record
temperatures and pressures every thirty minutes.
b. Start the electrowinning cell after the first bed volume -
thirty minutes running time.
c. After one hour in the elution step (06) the following
operating parameters are considered desirable.
Top of column temperature around 1 10°C
" M pressure around 130 kPa
Bottom of column temperature around 125°C
" " pressure around 300 kPa
Elution water pump pressure 270 to 300 kPa
Heat exchanger pressure in 170 to 190 kPa
" " pressure out 150 to 170 kPa
Thermocal temperature in around 125^0
" " out around 122~C
A falling top of column temperature is the best indicator
of possible trouble caused by such things as dirty heat
exchanger plates, thermocal heater not operating properly
or pegged inline screens.
3. 6 Transfer of Barren Carbon to Regeneration Kiln Hopper
a. Open the back up manual valve on the barren carbon transfer
1 ine .
b. Back flush the carbon transfer line into the quench tank by
attaching a hose to the minsup coupling behind the
dewatering screen above the feed hopper. This step is
only necessary if the previous lot of barren carbon was
transferred directly into the quench tank.
c. Close the carbon delivery valve above the quench tank.
-16-
d. Make sure that the dewatering screen is clean,
e . Fill the carbon transfer 1 ine by putt ing a hose on the
sample point and running it until an adequate flow of
return water is evident. Do not over flush as this could
flood the kiln.
f. Press the "stripped carbon transfer start' button and
throughout the transfer monitor: -
Ci) The flow of return water. Should this decrease
markedly, stop the elution water pump locally and
flush the carbon transfer line again. Restart the
transfer by pressing the "sequence start' button.
(ii) The bottom of column pressure. Should this rise
suddenly above 220 kPa, immediately stop the
elution water pump and repeat the procedure
outlined in <i> above.
g. Take regular samples throughout the transfer and label the
combined sample :-
"STRIP No. BARREN, DATE , activity and Au"
h. The alarm will sound at the end of the programmed transfer
time. Press the "alarm accept' button and then check to
see if the transfer is completed by:-
<i> Looking in the bottom sight glass.
(ii) Observing clear water only gushing from the sample
point .
(iii) Noting a marked increase in the flow of return
water . Wait for this before stopping the transfer
by stopping the elution water pump locally. This
is important as the increased flow indicates that
the carbon transfer line is flushed clear. Again
do not risk flooding the kiln by over flushing the
llT *e.
i. After stopping the elution water pump locally, reset the
switch and then reset the sequence controller by: -
<i) On the sequence controller panel, switch the L.H.S.
toggle switch to "m' and the adjacent toggle switch
to % out off 1 .
<ii) Pressing the white "reset' button next to the toggle
switches.
Clii) Pressing the blue "start* button and then putting
the toggle switches back to their original
positions.
-17-
3.7 ElectrowinninK
a. General
One bed volume (thirty minutes) after the commencement of the
elution step (06) the electrowinning cell may be put into
operation. When a strip is not in progress and the cell is
required to electrowin intensive cyanidation product, at
least 15 cubic metres of hot water should be pumped from the
column into the eluate tank beforehand,
b. Start Up Procedure
(i) Check the valves by the eluate tank.
(ii) Shut the drainage valve at the base of the cell.
<iii) Open the input valve partly.
(iv) Hake sure that the fume exhaust fan is operating. This
be left on at all times.
<v> Start the pump - it will not start if the local switch
outside the goldroom door has been left isolated.
(vi) Open fully the input valve.
(vii) When there is a flow over the weir at the discharge end
of the cell, switch on the rectifier and adjust the volts
to no more than 5.0; the amps will be around 600.
(viii) Regulate the input valve so that the eluate level is
about half way up the overflow outlet of the cell.
(ix) Monitor the cell regularly to check on both eluate level
and volts.
(x) Check the pH and cyanide levels. They should be around
12.5 and approximately 0.3% respectively.
(xi> Tell the night shift personnel that the cell is
operating. If there is a power failure, the pump will
need to be restarted at the local switch.
c . Shut Down Procedure
(i) Take an eluate sample. The assay should be <5 ppm, /Au
before shutdown and if there is time, <1 ppm. /Au.
(ii) Stop the pump - reset the switch immediately,
(iii) Open the dump valve on the line leading to the eluate
tank.
(iv) Vhen the cell is half empty, switch off the rectifier and
turn the control knob back to zero.
-18-
(v> Shut dt open the appropriate valves by the eluate tank,
<vi) Before pumping out the spent eluate to the process water
tank, advise both the intensive cyanidat ion operator and
the shift foreman.
Cvii) When the tank is pumped out , the eluate pump should stop
and the low level indicator will come on on the control
panel. Change the valves by the eluate tank back to the
positions required for e lectrowinn ing .
d. Points to Watch
1. High eluate level in the cell could indicate:-
(i) The cathodes are blocked with slime or fully
loaded .
<ii) The input valve is opened too far.
2. Low eluate level in the cell could indicate: -
(i) The pump is faulty,
(ii) The input valve is shut too far.
3. Incorrect voltage level could indicate: -
Ci) Too much resistance in the cathodes, i.e.
they are heavily loaded or slimed up.
Cii> Faulty electrical contact on the cell.
Ciii) Incorrect pH level.
4. Eluate is poisonous - wear gloves when taking a sample or
handling the cathodes. Do not linger by the cell even when
the fume exhaust fan is operating.
Tu/d Mintek design cells are used here for recovery of
gold by electrowinning from the eluate. hach cell has nine
cathodes and these can together load up to 70 kgs. of gold
Plate on about 3.5 kgs. of steel wool under good conditions.
-19-
3, 8 Stripping System - Optimization of Reagent Usage
a . Desired Reagent Levels
Acid Wash
Step 03 2% HCL
Stripping sequence
Step 02 2 to 3% NaCN
Electrowin ....sufficient NaOH for pH 12.5
b. Control of Reagent Addition
The reagent addition can be controlled by altering either the
pump speeds, i.e. by changing the pulleys, and/or adjusting
the dosing time that has been programmed into the sequence
controller, Altering of the pump speed is preferable in
cases where a change in the level of one reagent only is
desired on a permanent basis. Changing of the dosing time in
the stripping sequence (step 02) results in the changing of
the levels of both NaCN and NaOH as the same timer controls
both pumps. Should it be necessary for some reason to add an
additional amount of either reagent at the end of step 02,
e.g. is cases where the pressure relief valve of a particular
pump is faulty and reagent goes back into the tank, this may
be done by operating both the particular pump and the
relevant valves manually. Refer to section 2.4c of this
manual .
c . Example Calculation of Reagents Required for Stripping
Sequence Step 02
NaCN added 560 litres @ 15%
NaOH added 100 litres <3 49%
Volume of column . . 3900 litres
Bed volume
(1.9 tonnes) 3600 litres
of which 0.6 is occupied by aqueous phase.
Hence in the preheat step <05), available aqueous phase
= (3900 - 3600 litres) excess space in column.
+ (0,60 x 3600 litres) aqueous phase in bed volume.
+ 100 litres in external pipework
2560 litres.
NaOH added to preheat
= 100 litres x 1.5 (sg correction)
= 150 kgs.
Since it is at 49%, the total NaOH added
150 kgs.
«. = 73.5 kgs .
-20-
Level of NaOH in column
- 73, 5 x 100 = 2.9%
2560.
HaCN added to preheat (no sg correction required)
15. x 560 " 84.0 kgs.
100.
i
Level of NaCH in column
84. x 10 = 3.3%
2560.
Determining Optimum Acid Vash R insing Time
The acid rinse step (05) is currently set for 2.5 hours. This
could be excessive and wasting potable water. To determine
the optimum time it is necessary to take samples every
fifteen minutes from the rinse discharge line sampling point
at the top of the acid wash column.
These samples should be analysed for Ca plus Mg and then the
totals plotted versus time. When the curve flattens out, the
rinsing is sufficient (even if the pH is only 4). The
sequence controller time for step 06 should then be reset to
the time indicated by the graph.
-21-
FAET 4 - THE STRIFFING SYSTEM - FAULT FINDING
4. 1 Acid Wash
Problem
Possible Cause
b. Acid wash
start .
will not
Carbon does not Ci> Valve AV 401 not open,
enter column. <ii) Valve AV 414 not open.
Ciii) Carbon hanging up - put more
water in hopper,
(iv) Blocked screen in top of
column.
<i> Fill selector switch not on
manual .
<i> Valve AV 414 not open.
Cii) Blocked screen in top of
column.
<i> Pump pressure relief valve
stuck open.
Cii) Valve AV 404 not open.
Ciii) Feed valve to pump not open.
<iv) Blocked inline screen before
pump.
<v) Water pump stator damaged.
Cvi) Acid pump faulty.
Points to Watch
1. Clean the inline strainer at the top of the column
regularly.
c . Column pressure over
200 kPa,
d. No discharge during
acid injection or
rinsing
2. Watch the column pressure - if it exceeds 200 kPa
screen in the top of the column may need cleaning.
the
3. Check the discharge sump during acid injection and
rinsing.
4. At the end of the rinse stage the discharge water should
have a pH level of >5.
4 . 2 Transfer of Loaded Carbon to Elution Column
Possible Cause
Problem —
—
a. High elution column Ci) Blocked inline filter bag.
pressure. ( ii ) Valve AV 415 not open.
Ciii) Transfer line to potable water
tank blocked.
-2Z-
b. High acid wash
column pressure,
(but not elution
column pressure. )
c. No water discharg-
ing to potable wat-
er tank.
(i) Carbon transfer valves AV 406
and/or AV 422 not open,
(ii) Carbon transfer pipe blocked.
(i) Valve AV 415 not open.
( ii) Water pump feed valve not
open .
(iii) Water pump stator damaged,
(iv) Water pump not running.
Points to Watch
1. The filter bag at the top of the elution column should be
cleaned out after each carbon transfer.
2. Make sure that the acid wash column is empty at the end
of each transfer.
3. Watch the pump pressure - it should not exceed 350 kPa .
4. Watch for water discharge to the potable water tank
should start after the elution column fills with water.
5. Don't forget to take incremental samples from the carbon
transfer line sample point.
4.3 Reagent Addition an d Preheat StaRe
Problem Possible Cause
a . High column press-
ure during reagent
addition.
b. Reagent pump
relief valve by-
passing fluid.
c. Elution water pump
cavitating.
d. Heater stops.
e. High column Press-
ure.
(i) Valve AV 416 not open,
(ii) Blocked line to eluate tank,
(iii) Inline filter bag dirty.
(i) Blocked reagent line,
(ii) Valve AV 410 not open,
(iii) Pressure relief valve faulty.
(i) Blocked screens in bottom of
column.
(ii) Dirty heat exchanger plates,
(iii) Airlock in top of column.
water
pump
not
(i) Elution
running,
(ii) Thermocal pump not running,
(iii) Thermocal pressure low.
(i) Temperature at top of column
too high. (Preheat
temperature should not exceed
90 =c>
(ii) Heat exchanger plates dirty.
-23-
Polnts to Watch
1. Whilst the reagent pumps are operating check that the
pressure relief valves are not bypassing any fluid and
that the flow meters are operating.
2. Check the bottom of column pressure - it should not
exceed 350 kPa.
3. Watch the elution water pump pressure relief valve for
any liquid discharge.
4. Make sure that no solution is leaking through the carbon
transfer valve AV 421.
4.4 Elution and Carbon Cool
Problem
Possible Cause
a. Stable elution temp- (i) Heat exchanger plates dirty
era t ure be 1 ow
1 lO^'C from column.
<ii> Elution water pump flow rate
too high.
Ciii) Preheat not brought up to
desired column top temperat-
ure - 90°C).
b. Stable elution temp-
erature over
115 C 'C from column.
<i> Flow rate of water too low.
<ii) Thermocal temperature too
high.
Points to watch
1. Maximum thermocal temperature should not exceed 125~C.
2. Throttling valve should be adjusted to maintain bottom of
column pressure at 300 kPa during the elution.
3. The elution water pump flow rate should be between 110
and 120 1/min.
4 . 5 Transfer of Barren Carbon to Regeneration Kiln Hopper
Problem
Possible Cause
a. High column pressure. <i) Valve AV 421 not open.
<ii) Blocked carbon transfer line.
b. No discharge to kiln
dewatering screen.
(i) Valve AV 409 and/or AV 412 and
/or AV 421 not open,
<il) Elution water pump feed valve
not open or inline screen
before it blocked.
-24-
-25-
i
FART 5 - THE GRAVITY CIRCUIT
5. 1 General
The gravity circuit is designed to extract "coarse gold' from
the recirculating load in the mill grinding circuit and hence
prevent a build up within that circuit and the eventual escape
of some of that gold into the C.I.L. tanks and thereon into
the final tails. (See fig. 4>'
5. 2 The Spirals
a. Optimum Operating Conditions
For the spirals to work efficiently the feed supply must have
consistent characteristics and be of a constant rate.
Variations in the flow rate, the feed size distribution and
percentage solids will have adverse effects upon separation.
Generally the solids tonnage should give adequate loading of
the concentrate and middlings areas and the pulp density
should be low enough to ensure mobility of particles in these
areas.
I
i
Feed to the spirals may be adjusted by the moving of two
splitter arms on either side of the cyclone underflow
discharge box, this altering the volume of the feed passing
over the splitter screen. (See fig. 5)
I
1 —
\ /
Cyclone
U/F dis- \
charge boy^
r
To mill
To splitter ' To mill
screen feed
Fig, 5 The Gravity Splitter Box
Splitter
arm may
be moved
in either'
direction
With bungj
in place
C/U dischpr
fills box k
pulp floWb
over sides
i
The feed may also be adjusted by varying the speed of
gravity feed pump. This is necessary when the mill feed
been dropped and it Is impossible to get sufficient feed
the gravity pump by adjustment of the splitter arms. At such
times the speed will need to be dropped and the water addition
the
has
for
l
I
I
i
i
-26-
adjusted to provide optimum feed density.
The pulp density may be altered by the addition of water,
before the splitter screen, in the gravity feed pump hopper or
to the concentrate launder beneath the prima ray spirals. The
latter option adjusts the density of the feed to the cleaner
spiral only.
The Static Distributor <See fig. 6 )
The static distributor at the head of the primary spirals
ensures an accurate division of the pulp stream to the
spirals. For maximum efficiency a constant head should be
maintained in the head pot. The head can be adjusted by either
altering the flow rate from the splitter screen and/or
altering the annular gap between the head pot and the
distributor body, by moving the head pot up or down as
required. |
The Primary Spirals
Feed from the splitter screen passes down into the gravity
feed pump hopper and from there it is pumped to the static
distributor above six triplex type primary spirals. As the
pulp passes down these spirals; separaration of particles
occurs according to specific gravity and the heavier minerals
progress to the inner profile while lighter minerals are
forced towards the outer profile, along with most of the water
and slimes. At the bottom of each spiral layer there are
splitters which can be adjusted to ensure the optimum recovery
of * coarse gold' . (See fig. 7)
The Wilfley Table Requires
Constant Monitoring.
-28-
d. The Cleaner Spiral
The middlings and tailings from the primary spirals are
The proportion going to either may be adjusted so as to help
achieve optimum grinding conditions. P
The concentrate from the primary spirals is fed on to a duplex
cleaner spiral. This spiral operates in exactly the same way
as do the primary spirals. y
The concentrate from the inner outlet of the cleaner spiral is
tailin^ C re^ °? J° 25 V±lfley taMe ™ d the middlings and
mill d?i.h t0 t ^ « ravit y SU »P P^P which feeds info the
mill discharge pump feed hopper.
e. Mainten ance of the Sp irals
(D for ZZt* ° f the * s P irals sil °uld be regularly checked
-L UI Wear <
<11) The spirals should be hosed down on a daily basis.
(iii) The spirals should be adequately flushed before a
shutdown and then hosed down immediately afterwards
SO mm to Prevent a build up of solids on the spiral
— i* the static
5-3 The Vilfley T.hl.
a ■ General Description (See fig, r>
Wash sprays
corner
Fig. 8 The Vilfley Table
-29-
The Wilf ley table is a standard No, 12 right hand version. It
is a mechanically operated reciprocating action table,
consisting of a self -oiling enclosed type of head motion, a
partly riffled rectangular deck and an understructure with
tilting device for the table.
b. The Head Motion
The head motion is a self-oiling Pitman and toggle type. The
motion is created by an eccentric shaft acting on the Pitman
, with one toggle set and the other toggle connected to a yoke
driving the table through a connecting rod. (See fig. 9)
Fig. 9 The Head Motion
This type of motion forms an uneven stroke, slowest at the
end of the backward stroke and having increased acceleration
towards the end of the forward stroke. (See fig. 10)
1. Beginning of Forward Stroke
2. End of Forward Stroke
3. End of Backward Stroke
Fig. 10 The Stroke Pattern
-30-
Ad.1 ustment of the Deck
(i> Longitudinal Level: The inclination of the table
lengthwise may be adjusted by the raising or
lowering of the rocker pockets at each end of the
deck. (See fig, 11)
Fig. 11 The Rocker Pockets
<ii) Tilt of the deck; The deck may be tilted sideways,
i.e. across the riffles, by way of a hand wheel that
is connected to a gear which drives bolts
attached the bolsters on which the rockers
supporting the table are located. <See fig. 12) The
forward bolster is linked to the main frame by a
tension bar that removes any vibration from the
concentrate end of the table.
Table Frame
Hand Wheel-*
Bolster
Rocker Pocket
Fig. 12 The Tilting Mechanism
(ill) Vater VashL The feed edge of the table (See fig- 8)
has a water spray bar. This water is adjusted so
to provide a gentle wash across the table.
-31-
Act ion of the Table
The action of the table creates inverse classification and
stratification, i.e. each mineral of a certain specific
gravity is arranged according to size. (See fig. 13)
Riffle
O'o'p <^. •-
* O • o c o O'
O • ' o * o « • *
Stratum
Table top
Fig. 13 Inverse Classification and Stratification
Due to the motion the bed moves to the concentrate end. As the
height of the riffles decreases towards this end of the table
lighter gangue loses the support of the riffles and the wash
water carries it towards the lower side of the table into the
tails and this then concentrates the remaining heavy mineral.
The heavy mineral then moves on to a smooth plane where any
fine gangue and larger particles easily rolled by water are
washed from the concentrate.
Operation of the Table
Feed to the table should be around 25 to 30% solids. If the
percentage solids is too high the table may become bogged and
separation impaired, this resulting in portion of the heavier
material being allowed to pass directly across the table into
the tailings launder. Application of wash water should be
sufficient to provide a gentle, even flow over the table
without the development of heavy riffles across the deck.
Notice should be taken of the type of feed presented and the
table must be adjusted to ensure optimum separation. Slimes
will require a short, fast stroke with the tilt not far from
the horizontal whilst coarse feeds will require a long, slow
stroke with a steep inclination, (tilt)
The longitudinal level of the deck may also need to be
adjusted to cater for different feed characteristics. This is
done by raising or lowering the rocker pockets at each end of
the table. Very fine feeds (-175/t* ) may require the table to
be level longitudinally whereas very coarse material may
require the concentrate end of the table to be up to 19mm
higher than the feed end.
If the table is operating properly there should be a notable
classification of "coarse gold' and the gangue at the
concentrate end of the deck with the line of separation coming
along the diagonal ending of the riffles and terminating near
the concentrate discharge corner of the table. (See fig. 14)
-32-
Tails
Fig. 14 Lines of Separation
The Quality of the concentrate recovered may be regulated by
the movement of the splitter above the concentrate launder.
(See fig. 15)-
Fig. 15 Concentrate Launder and Splitter
Maintenance of the Vilflev Table
(1) The head motion drive box should be kept topped up
to the required oil level,
Cii) The rocker arm pockets should be kept free of
foreign material and topped up with oil.
<iii) The table should be kept clean, i.e. no build up
should be allowed.
<iv) All parts including the drive belts should be
checked on a regular basis for wear.
-33-
5. 4 Starting Up and Shutdown Procedure for the Gravity circuit
a . Start Up
<i) Start the gravity sump pump.
Cii) Start the Vilfley table.
(iii) Put a bucket below the concentrate launder.
Civ) Turn on the raw water isolating valve. The 50mm ball
valve is accessible from either inside the gold room
or from the first landing on the stairs leading up to
the stripping plant control panel.
(v) Ask the mill personnel to put the bung in the cyclone
underflow discharge box.
(vi) Turn on the water addition valve above the gravity
feed pump hopper .
Cvii) Start the gravity feed pump.
(viii) Check that the gravity circuit is operating properly.
It may be necessary to adjust the feed and/or the
water addition points.
b. Shut Down
(i) Ask the mill personnel to take out the bung in the
cyclone underflow discharge box and also to flush out
the gravity feed line and pump hopper. It is
preferable that the flushing continue for five
minutes at least.
Turn off the water addition valve above the gravity
feed pump hopper.
Ciii) Stop the gravity feed pump.
(iv) Close the raw water isolating valve,
(v) Stop the Vilfley table. Mill personnel may do this by
isolating it at the gold room switchboard - during
night shift only.
(vi) Stop the gravity sump pump.
(vii) Hose down the spirals.
-34-
FART 6 ~ PREPARING QF GRAVITY CONCENTRATES FOR SMELTING
6 . 1 General
The final concentrate taken off the Vilfley table Is not
suitable for direct smelting. The " lines of separation* as
shown in fig. 14 (PartS) are not always clearly defined as
there is some intrusion of impurities, namely steel, into the
concentrate zone and likewise some gold finds its way into
the middlings. It is therefore necessary to include part of
the middlings with the concentrate in order to prevent loss
of too much coarse gold back into the circuit via the
tailings launder.
Hence before the concentrate can be smelted it must be
further upgraded. This may be done by purely mechanical
means, e.g. re-runs over the Vilfley table, but such methods
will invariably also result in the loss of some gold back
into the circuit and also require additional labour.
It is preferable that all of the gold in the Vilfley
concentrate be retrieved. Two traditional methods of
achieving this are Amalgamation and Acid Digestion. Both
methods have been practised throughout Australia for many
decades and likewise both offer very good recovery if
efficiently employed.
6 . 2 Amalgamation
This method involves the exposure of gravity concentrate to
mercury in a rotating, fully sealed barrel. The mercury
amalgamates with any free gold and this product is then
separated from the remaining waste for later retorting.
Retorting simply involves the heating of the amalgam so that
the mercury vaporizes and passes into a condenser barrel
leaving the gold "sponge' behind.
This method is extremely efficient but in recent years the
use of mercury with its associated danger has been frowned
upon. Hence amalgamation has been rejected as a viable
alternative here and for this reason it will not be covered
in detail within this manual.
6. 3 Acid Digestion
This method, as used here from the commencement of
operations, involves the burning away or "digesting' of
impurities by exposing the concentrate to very strong acid
solutions. If handled properly it can produce a very pure
upgraded concentrate for smelting. It is however subject to
censure on four accounts: -
<i) It involves the use of highly dangerous acids.
(ii> The Vilfley concentrate must be upgraded by mechanical
-35-
means, i.e. as employed here the re-running of it over
the Vilfley table, so as to get rid of some of the
impurities and in so doing reduce the quantity of
concentrate to an amount that may be efficiently treated
by acid digestion.
(iii) Acid digestion does present a security risk in that the
daily upgraded product is of a very high quality and its
form is such that some could be very easily "siphoned
off ,
,(iv) Some loss of free gold may occur during the decanting off
of acid and subsequent rinsing.
It is basically for the above reasons that the use of a more
recent development "Intensive Cyanidation' is being
experimented with. However as acid digestion has been
practised for so long here, a step by step procedure has been
outlined below.
. Re-run the concentrate for a twenty four hour period over the
Vilfley table in order to both upgrade the concentrate and in
so doing reduce it to an amount of no more that 10 to 20
kilos.
Expose this in a large container to hydrochloric acid using
approximately two litres of acid to every kilogram of
concentrate. Stir regularly.
Vhen the activity has ceased, decant off the acid, via
another container, and then rinse the concentrate at least
four times by filling the concentrate container with water
and stirring; and decanting off each lot of rinse water.
Put half a bucket of water into the concentrate container and
then gradually introduce one bucket of nitric acid. Continual
stirring is required during this stage and care must be taken
to prevent frothing over and loss of concentrate.
Vhen the activity has died down, put the entire
concentrate/acid solution mixture into the mechanically
agitated vessel and leave it there for at least ninety
minutes. This will ensure that all of the concentrate comes
into contact with the nitric acid.
Decant off the acid, again into another container.
Kinse the concentrate thoroughly at least three times;
decanting off each batch of rinse water into another
container .
Should there be any precipitate in the concentrate, this will
indicate that not enough nitric acid was used. This can be
easily broken down by exposing it to sulphuric acid. Use a
50/50 acid/water mix and put the water into the container
-37-
first. Only a very small quant it iy of acid is required -
possibly no more than one to two litres at the most. After
the precipitate has become entirely fluid, fill the container
with water and stir well before decanting off the solution
and rinsing the concentrate.
i. Dry the concentrate and after recording the weight, lock it
up in the strongroom.
Points to Vatch
1. All of the acids are extremely dangerous! Wear protective
clothing and a full face mask fitted with a cartridge
filter suitable for use in areas exposed to organic acid
fumes.
2. All of the digestion work must be carried out under the
fume extraction hood.
3. Make sure that the water to the scrubber has been turned
on.
4. Rinsing between the hydrochloric acid and nitric acid
applications must be very thorough. The two acids when
combined will dissolve gold and result in loss whilst
decanting off,
5. Any sediment from the containers decanted into must be
returned to the concentrate container at each stage.
6 . 4 Intensive Cvanidation
a. General
The upgrading of gravity concentrate for smelting purposes by
use of intensive cyanidation is still in the experimental
stage. It involves the leaching out of the gold into
solution, using a strong cyanide mix, and then the
electrowinning of that solution so as to recover the gold on
the steel wool cathodes. This system is capable of handling
all of the initial concentrate off the Vilfley table.
Because of physical limitations of the present ^pilot plant 1
it is necessary that the concentrate cut off the Vilfley be
limited to 100 kilos every twenty four hours, this being the
optimum amount that can be treated efficiently in the
leaching vessel. Hence it is necessary for the table to be
monitored on a regular basis so as to ensure that not too
much gangue gets into the concentrate,
b. Description of the Plant (See Fig. 16)
The Leach Vessel
This vessel has a capacity of 0.75 cubic metres. It is fitted
with an air sparge and an air operated agitator that has two
sets of blades, one set located near the bottom of the vessel
and the other midway in the optimum charge. The vessel is
also fitted with baffles and the floor is sloped towards the
50 mm dump valve, A 25 mm decant valve is located 230 mm from
the base of the container.
The Filtration System
The loaded product from the leach vessel is drawn through the
decant valve into a primary bag filter (75 microns) and then
pumped through a secondary bag filter (1 micron), this
removing most of the foreign material before the solution -
enters the holding vessel.
The Holding Vessel
This vessel is identical to the leach vessel but it has no
baffles in it and it is not agitated. It allows the accurate
measurement of the loaded leach and rinse solutions and also
acts as a storage vessel should it not be convenient to pump
the solutions into the eluate tank. Solutions from the
holding vessel may be either gravity fed directly into the
eluate tank or pumped to it via the filtration system.
. Operation of the Plant
Charging the Leach Vessel
<i) Fill the vessel with potable water to the 300 litre mark.
<ii) Add 6 kgs. NaCN and agitate for around 15 minutes,
Ciii) Put in the concentrate - around 100 kgs.
(iv) If necessary add NaOH to attain a pH level of >11.
<v) Rote the level of the solution on the vessel. Fill to the
same level when putting in subsequent leach and rinse
solutions.
<vi) Start the agitator,
(vii) Adjust the air sparge to 10 kPa.
Optimum Treatment Time
The duration of each leach and the number of leaches required
depends largely upon the quality of the concentrate being
treated. The first leach solution loads up very quickly and
it is advisable to change it after no more than three hours
operation. Hence if a charge is put into the leach vessel
late in the morning it should be changed mid afternoon and
the final leach left in overnight. Generally only two leaches
are necessary with the present plant.
-39-
Rinsing and Further Leaching
<i) Stop the agitator and allow the solution to settle.
(ii) Decant through the filtration system into the holding
vessel .
(iii) Note the level on the holding vessel and record it on the
log sheet.
(iv) Take a sample and filter it. 150 mis. to go to the
laboratory for assaying; and the pH and cyanide levels
to be recorded on the log sheet.
<v> Fill the leach vessel up to the original mark and agitate
the solution for 15 minutes.
Cvi) Check to see what stage the current electrowinning is at.
If o.k. pump the holding tank out through the filtration
system, into the eluate tank.
(vii) Stop the leach vessel agitator and shut off the air
sparge. After settling, pump the solution into the
holding vessel. Take a sample for assaying.
<ix> Fill the leach vessel up again as per section "Charging
the Leach Vessel" but do not put any additional
concentrate in and only use 4 kgs. of NaCN, Check to see
that the pH level is >11.
Cx) The leach and rinse procedures outlined above are to be
repeated for the desired number of times. Always be sure
tfl * ^m ple of both lea nh and rinse solutions, and
to record the quantities of each, and the pH and cyanide
levels of leach solutions.
One rinse must be done between leaches and two rinses
done after the final leach.
Dumping of Barren Concentrate
(i) Open the 50 mm dump valve on the leach vessel. This
allows the barren material to go back over the VI If ley
table and ensures that any coarse gold, that has not
been completely dissolved in the leach vessel, will not
be able to escape directly back into the circuit.
<ii) Hose out the vessel and then close the valve.
Points to Remember
1. For bullion accounting purposes accurate recording is
essential. Make sure that the following are completed: -
(i) Record the quantity of each leach solution.
Cii) Record the quantity of each rinse solution,
(iii) Take a sample of every leach and rinse solution for
2. Record the amount of reagents used for each leach.
3. Record the operating times.
4. Close the valves after each transfer from either the leach
or holding vessel .
5. Check to see that it is o.k. before pumping out the
holding tank.
6. When there is no strip in progress, fill the eluate tank
with at least 15 cubic metres of hot water from the
elution column before starting up the electrowinning cell.
This aids the electrowinning process and also helps to
ensure that any sludge that may have settled on the bottom
of the eluate tank is not disturbed.
7. Check out the filter bags regularly. It is imperative
that no solids be allowed to enter the eluate tank.
8. Cyanide and Caustic are very dangerous! Always wear gloves
and safety glasses when working near the plant. The fume
exhaust fan should be left operating at all times.
9. Should there be a power failure during an intensive
cyanldation process, only go near the plant if it is
absolutely necessary and make sure that you are wearing an
appropriate mask, i.e. one that is fitted with a cartridge
filter suitable for use in cyanide fumes. Remember that
there is no water for washing in during a power failure.
10. The pilot plant is located almost directly over the
barring furnace. Absolute care must be taken when handling
fluids so as to ensure that they don't splash or seep on
to the ground floor.
d. Further Considerations
Vithin the constraints offered by the physical inadequacies
of the present leaching vessel, it can be asserted that
"intensive cyanidation' is a feasible alternative to the "acid
digesting' of gravity concentrate. However problems are
occurring as a result of the input of intensive cyanidation
product into the electrowinning system. The cathodes are
being clogged up with precipitate and at the time of printing
this manual, two cells were in operation instead of the
normal one and all of the cathodes were being changed at
least twice a week. In the past it has been possible to load
at least 70 kgs. of gold on to one lot of cathodes in a
single cell, i.e. nine cathodes, with no ill effects upon the
operation of that cell.
This problem will have to be overcome as at present too much
additional handling of cathodes and cleaning up of sludge
build up within cells is necessary. In addition the
subsequent acid digestion and rinsing of loaded wool is made
difficult by its sludgy nature. Great care is required in
order to prevent loss of product back into the C.I.L.
circuit.
Obviously the benefits of being able to forward the loaded
solution from intensive cyanidation to the electrowlnning
system are great in terms of both cost and labour savings.
Less strips are required each week and this results in
substantial cutbacks in the use of reagents, water and gas;
and if the present electrowlnning problems are overcome, a
high grade product for smelting is ensured.
Goldroom ForGman, Ron Wilson, demonstrates
how easy it is to control a heavy container
on The Granites patented decant platform.
PART 7 - F PKPABIWG C ATHODE WOOL FOR SMELTING
7 . 1 General
diverted to the spare cell.
7.2 Removing the Vool
a Dump the solution in the cell by opening the drain valve on
the line leading back to the eluate tank.
b. Allow the cathodes to drain for about ten minutes.
c. Kemove each cathode from the cell and place " £
unloading table - ensure that there is a large conxam
under the discharge slide.
d. Undo the wing nuts and remove the copper contact bar.
e. Cut away the section of unloaded wool and put the remaining
loaded wool into the container.
f. When all of the cathodes are unloaded, weigh the wool.
7, 3 Add Dige stion of the Vool
a. Put on appropriate safety gear - organic acids mask and
rubber gloves.
b Place the wool in equal amounts into two large containers and
place these on the decant platform. (See fig- 17)
Adding Container
Sits Inside Tilting
Deck.
. 17 The Decant
-43-
c. Put a 4:1 mix of HCL and water in each container. Normally
two buckets to half a bucket in each container. This
quantity ensures good contact with all of the wool. Put lids
on the containers.
d. Stir up the wool regularly.
e. When the wool has broken up completely, the acid solution may
be decanted off into buckets. Allow this solution to settle
before decanting the buckets off into the acid area sump-.
Retain any sludge left in the buckets.
f. Fill up each container with raw water, stirring up the wool
thoroughly as this is done.
g. Decant off the water into buckets and allow to settle before
decanting the water into the gravity sump. Retain any sludge
left in the buckets.
h. Repeat the rinse/decant process at least three times - the
rinse water should become quite clear.
7 . 4 Drying the Cake
a. Line the large drying tray with newspaper - helps prevent
cake from sticking to the metal.
b. Place the tray on the hot plates and switch the controller to
the * 4 1 setting. Do not put on the top setting as it is
important that the hot plates don't get red hot.
c. Place the wool from the final decant in the tray - in an even
layer. Put any sludge from the decant on top.
d. Make sure that the fume exhaust fan is operating.
e. Stir the cake up at regular intervals to facilitate drying,
f. Do not over-dry; it is better if the cake is left slightly
damp as this helps prevent the loss of fines, When it is
dry enough remove the cake from the tray and after weighing
it, lock it up in the strongroom. Do not leave it outside
of the strongroom The Granite's C.I.L. cake is virtually
pure gold/silver - the shrinkage during smelting amounts to
less than 5% normally.
g. Switch off the hot plates.
Latching Mechanism as modified Counter Weights
by Herman Buhler in accordance with
design by Ian Williams
Lifting Device designed and
made by Herman Buhler. It makes
the handling of loaded moulds
much easier.
FART 8 - SMELTING
8. 1 The furnace
A tilting type barring furnace is used. It is heated by L.P.
gas and the specified maximum rated output of the burner is
achieved with a gas pressure of 140 kPa. It is presently
operated an 13 5 kPa, i.e. the maximum attainable pressure from
our supply system.
The advantages of using this type of furnace relate mainly to
safety and ease of handling. The crucible is fully enclosed
even during the pour hence the risk of injury to the operator
during a pour is considerably lessened in the event of a
mishap. Pouring is relatively easy, a virtual one man
operation provided that the furnace has been properly
Fig. 18 The Barring Furnace (Inset - Burner Unit)
The only real problem with this type of furnace is that the
changing of crucibles is a major task requiring the removal
of the furnace lid and extensive fireclay work. Smelting is
normally done of a Tuesday. Should a crucible failure occur
during the first smelt it would be virtually impossible to
put in a new crucible in time to get the gold out on
Wednesday as the furnace must be allowed to cool before doing
any repair work.
8 , 2 Crucibles Used
A 100 graphite based crucibles are currently being used.
These have been good for about 20 to 25 smelts in the past
but they are prone to attack by nitre. Of recent months
around 50% of the gold has come from the gravity circuit and
whilst the acid digestion of the concentrate from the Vilfley
table has improved, it has nevertheless been necessary to use
more nitre when smelting that concentrate. With the
refinement of the intensive cyanidation system this problem
will be avoided as most of our gold will be plated out on
cathode wool.
However a silica based crucible will shortly be installed.
These are twice as expensive as the graphite based crucibles
but with them as much nitre as is required may be used
provided that there is an excess of silica in the charge. Any
iron in the charge will combine with silica used in the flux
to form ferrous silicate. If insufficient silica is used the
iron will combine with the silica in the crucible and
eventually cause its failure.
The normal charge (cake + flux) is usually no more than
30 kgs. , this assuming that the standard 2:1 (cake: flux)
mix is used. It is good practice to vary the size of the
charge as this helps to prolong the life of the crucible.
8. 3 Moulds Used
The size of the bullion bars is limited by the capacity of
the moulds. The moulds used here have a capacity of around
23 kgs. However for ease of handling within the despatch
system, it is desirable that the bars do not exceed 19 kgs.
8 . 4 Fluxes Used
The fineness of the bars poured here is
being very little difference between the
C. I.L. bars and gravity bars in recent
fluxes used here are : -
very good, there
Mint assays for
months. The main
Borax
Boric Acid
Silica Flour
Sodium Nitrate
helps collect iron and i
agent .
helps collect iron but
smelt than borax,
provides silicon for slag
collect iron.
Strong oxidising agent - oxidises iron but
very damaging on crucibles if used too
generously.
good fluidizing
gives a thicker
and helps
Fluidizes slag but works against nitre
-47-
Vith the development of the intensive cyanidation system in
the future it will be possible to use a standard flux mix. In
the past it has been necessary to use more sodium nitrate
and silica flour when smelting gravity gold.
8. 5 Smelting Procedure
a. Fire up the furnace at least one hour before charging the
crucible. For the first thirty minutes keep the gas pressure
below 30 kPa and the air addition regulator closed. Fifteen
or so minutes before charging turn the gas up to maximum and
open up the air regulator fully.
b. Divide up the total cake into convenient smelting lots. Avoid
having very small smelts.
c. Mix the fluxes according to desired percentages of each,
making sure that they are thoroughly blended and all of the
lumps broken up. Wear a mask and gloves when handling flux.
d. Mix the cake and flux together (currently 2:1 mix) and then
pour the total charge into paper bags. This helps to prevent
loss of fine gold and makes it easier to load the crucible
when the furnace is hot.
e. Turn off the flame - do not attempt to load the crucible
whilst the flame is burning.
f . Load the crucible and put the cap over the charging hole.
g. Put the gas on maximum and open the air regulator up fully.
Put the stirring rod on top of the furnace.
h. Monitor the smelt regularly. When the charge liquifies it
will be necessary to stir it at regular intervals. Make sure
that the rod is red hot beforehand.
i. Warm up the mould - do not over heat - then position it on
the sand tray so that it is quite level.
j. Coat the mould with castor oil just before the pour. This
prevents the gold from sticking to it.
k. The smelt will be ready for pouring when the surface goes
flat and there is no movement, i.e. the charge is in a state
of ^quiet fusion' . Beware of bubbling around the edge of the
crucible - it could mean that the charge needs stirring and
it could also mean that the nitre is eating into the crucible
wall. The charge will be quite fluid when ready to pour. On
an average the first smelt takes ninety minutes and every one
thereafter around sixty minutes. (The furnace has by the end
of the first smelt achieved its maximum heat. )
-48-
sm^l? i« 2 h 7 C i° thln S and shield and then pour the
smelt in a steady stream. There must be two p P n p1o present
at each pour. (For safety and security reasons) '
m. Allow the loaded mould to cool until the slag has set.
^ mould 1 " SlOVSS and Susses - then break the bar out of the
o. If necessary, immerse the bar in nitric acid 50:50'
(nitric: water) mix to aid the cleaning process.
p. Scrub the bar with a wire brush, using soda ash and water.
^ number ^eV^S^' °S °* the bar and tte
number, e.g. 0696' on both top and bottom.
r. Weigh the bar and lock it up in the strongroom.
t. Clean away the slag after each pour and check for prills
Any prills found should go into the next smelt. F™"«-
MoleLn^ *££ reC ° rd thS tor details in the ~Gold
.J»«* inform the office so that the
arasfys saKSKsu " check the weishts and lock
" bo t th t c: Bl lTnat 1 ions Safety **" * *** — lock
W ' tLrnL h w d * °* eaCh ,. S1Delt check out *»»• crucible
tiZ^ K 7 rrf- USe the cali P«^s to compare the wall
thickness with that of a new crucible.
8.6 Points to Watch
1. Beware of fumes - these can be extremely toxic
Fortunately The Granites cake is very clean.
2 ' smelting"* ° XySen res P^ator before commencing
3
Keep liquids away from the furnace. Keep the floor dry.
4. Keep the goldroom doors locked and make sure that all
™5 T 5 sl * ned in ' to sure that they fully
understand the rule, ^hands off. 7
-49-
PART 9 - CARBON REACTIVATION
9 . 1 General
Fouling of carbon with associated deactivation is fairly
rapid in C.I, P. circuits. Acid washing and elution only
partially reactivate carbon and so for its repeated use,
thermal reactivation after each loading is essential.
Reactivation kilns are basically of two types; rotary kilns
and vertical kilns. The use of rotary kilns is widespread
but generally they have proved to be more expensive in terms
of capital and maintenance costs and also they offer low
thermal efficiency, when compared with the more recently
developed vertical kilns.
The Granites Gold Mine opted for a vertical type kiln. (See
fig. 19) Many teething problems were encountered during its
first eight months of operation. These were mainly
associated with such things as, difficulty in dewatering the
carbon prior to its entry into the feed hopper, hanging up of
carbon in the feed hopper, fouling of the carbon transfer
heat tubes and poor electronic control. Most of these
problems have now been overcome.
Better control of the carbon transfer has ensured a moisture
content of <50% as per design requirements. This transfer is
now carried out after the kiln has reached operational
temperatures, this ensuring that much of the residual
moisture is vapourized off before it can enter the fire box
where in the past it has caused considerable damage to the
insulation.
The operation of the kiln was impaired for many months
because of difficulty in maintaining a constant feed. Build
up on the cone section of the feed hopper interfered with the
flow of the carbon into the kiln. This has now been partially
overcome by the cleaning of the metal surface and subsequent
coating of it with a Teflon film. In addition a small
vibrator was fitted to the side of the kiln.
A special reaming device was recently received from The
United States. When passed through the carbon transfer heat
tubes it effectively removes all build up and this prevents
to a great extent the hanging up of carbon within the tubes.
The electronic controls have now been completely modified. It
is the desired objective of our maintenance section to make
the kiln operation completely automatic, i.e. all that the
operators will have to do is put the carbon into the feed
hopper, press the " start' button, monitor the temperatures
and take regular samples for activity testing and finally,
press the -stop* button. This is of course an admirable
objective but unfortunately it may not prove to be entirely
practicable, A feature of this type of kiln is that the rate
Hxhaust Gas temperature
thermocouple probe.
Fire Port
x. ■
Approximate Arrange-
ment of carbon trans-
fer heat tubes viewed
from above.
Carbon Discharge
Syntron
Carbon Temperature
thermocouple probe
Sample Taking
Hatch
j
Quench Tank
Vedge Wire
Overflow Screen
— I
Fig. 19 The Carbon Regeneration Kiln
-51-
of carbon movement through it do«5 tend to vary, especially
during the early hours of each reactivation. During this
period it is desirable that adj ustments be made to the
discharge feeder setting and/or to the exhaust gas setting.
With the present system of controls a change in the discharge
feeder setting can upset the controls completely. It is
therefore essential that the operators fully understand
exactly what each readout display represents and what each
control does so that they are completely aware of the
consequences of making any adjustment.
9.2 Start Up Procedure (See Fig. 20)
a. If starting from cold, i.e. a new regeneration: -
<i) Make sure that the feeder switch (on the side of the
kiln control panel) is in the "on* position and
that feeder setting is on 5.25.
<ii) Press the "start' button.
b. If starting after a "high exhaust gas' temperature fault
light indicates: -
(i) Press the black "burner reset' button.
(ii) Press the "start' button.
(Ill) Check to see that there is a carbon discharge.
c. If starting after a "burner fault' light indicates: -
(i) Reset the black box controller - on the back of the
burner unit.
< ii ) Press the "start 1 button.
(iii) Check to see that there is a carbon discharge.
9. 3 L. E . D. Readouts
a. HiRh Exhaust Gas This is a safety device working off the
exhaust gas thermocouple probe. When the exhaust gas
temperature reaches the upper limit of the setting, e.g. as
illustrated on fig. 20 450 + 99~, the "high exhaust gas-
temperature light will come on and the kiln will shut down.
Restart as per 9.2b above.
b. Preheat Temperature Readout
This is a safety device designed to protect the kiln from the
impact of sudden heating. The burner will operate on "low
fire* until the preheat setting, e.g. lOO^C as illustrated
in fig. 20, is reached. During this period the green light
-53-
will indicate alongside the readout, When the preheat
temperature has been reached this light will change to red
and:-
(i) The discharge feeder will start.
Cil) The "high* fire will come on.
(iii) The vibrator will operate intermittently as per a
preset cycle,
c. High/Low Fire Control
If the carbon temperature falls below the set point, e.g. as
illustrated 720-C, the "high' flame will come on. When the
, temperature reaches the upper limit (720 + lO^C) , the
"high' fire will go out. The light by the readout will be red
when the high fire is off and green when it is on.
■ 4 Shutting Down the Kiln
(i) For normal "end of regeneration* press the red
^stop/reset' button at the bottom of the panel. The
fan only will continue to run for two hours.
(ii)'For emmergencies only, press the large red
"emmergency stop' button. Everything including the
fan, will stop. (Emmergency stop buttons will shortly
be installed in two positions a safe distance from
the kiln. The use of these buttons for anything
other than an emmergency will cause unnecessary
damage to the kiln and burner unit. )
■ 5 Adjustment of the Rate of Carbon Discharge
(i) Switch the "bottom feeder' switch to "manual'. The
feeder will then run continuously,
<ii) Adjust the feeder control setting on the box on the
side of the kiln control panel. Confirm the rate of
discharge by taking a physical sample aver 15 seconds
and multiplying its weight by 0.24 to obtain
kgs./hour The ideal discharge should be at least 85
kgs./hour and no more than 110 kgs./hour.
<iii) Switch the "bottom feeder 1 switch back to "auto* .
■6 Adjustme nt of Vibrator Intensity
(i) Switch the (vibrator) switch to "manual' . The
vibrator will then run continuously.
Cii) Adjust the vibrator control setting on the box on the
side of the control panel.
-54-
<iii) Switch the ^vibrator' switch back to "auto 1 .
9. 7 Points to Watch
a The rate of carbon discharge setting is critical to the
automatic cantrol mode, A sudden increase in the rate of
discharge will prompt the ^high' fire to come on and stay
on as it is governed by a probe in one of the carbon
transfer heat tubes. This will cause a rapid increase in
the ^exhaust gas' temperature and could result in a high
exhaust gas* temperature shut down,
t
b. When the exhaust gas temperature readout is very high
slow the feeder down and monitor the temperature
continuously. Should it be constantly too high with a
normal carbon temperature (around 720~C> and likewise
normal discharge rate, it may be necessary to get the
electricians to increase the exhaust gas setting.
readout plus the upper limit should never go above
580~C.
c. Should it be suspected that the carbon is sticking up in
the tubes it is permissable to turn up the discharge
feeder, e.g. from 5.25 to 5.5, until such time as the
carbon runs more freely.
d. Honitor the kiln regularly. Take hourly samples and label
the combined sample: -
mrEGEN. NO. STRIP NO. DATE Activity"
e. Fill in the regeneration log sheet every hour.
f Do not let the kiln run empty as is is necessary to have
carbon in the tubes for the next start up The
regeneration should be stopped when the carbon in the feed
hopper is just above the drainage gutter. (See fig. W I*
is not advisable to leave the cone section covered with
carbon as this may result in a build up on the metal
surface and subsequent impediment of carbon flow into the
kiln. It is hoped to have a low level cut out fitted to
the kiln feed hopper soon.
-55-
FART 10 - GOLD ROOM GENERAL
10.1 Other Goldroom Duties
a. Loading of cathodes.
b. Sweeping/hosing of gold plant area.
c. Maintaining a stock of bullion boxes.
d. Carrying out repairs to the barring furnace.
e. Re-stocking of fluxes.
f. Re-stocking of reagents.
g. Reaming out of the regeneration kiln heat tubes.
h. Cleaning of the heat exchanger plates.
i. Checking of the thermocal level in the expansion tank and
topping up when necessary
j. Cleaning of the inline screens before each of the gold
plant pumps.
k. Cleaning out of the electrowinning cell, eluate tank and
potable water tank when required,
i. Cleaning of screens in both columns and the quench tank
m. Cleaning out the sump pump pits.
n. Regular hosing down of the spirals.
o. End of period stocktakes.
p. Monitoring of the condition of all plant and seeing that
the required maintenance is carried out.
10. 2 Security
It does not matter how honest employees are, if gold is
deemed to be missing, ALL persons will be potential suspects.
Avoid the possibility of this by observing the fallowing
rules.
a. Keep the goldroom doors, the strongroom and safe doors
locked.
b. Do not leave any cathode cake, gravity concentrate or
-56-
smelted products unattended. Lock them up in the
strongroom when they are not due for immediate handling.
c. Maintain very precise records of the movement of all cake,
gravity gold and smelted products.
d. Maintain very precise records of stripping and in
particular the intensive cyanidation operations. Vith the
introduction of intensive cyanidation, daily accountability
f is difficult. In most instances it will not be possible to
relate input to output, i.e. head grades with final
product, until completion of smelting every Tuesday; under
the past acid digestion system there was a degree of daily
accountability.
e. Good sampling is essential! All intensive cyanidation
leach and rinse batches must be measured and assayed.
Loaded and barren carbon samples must be taken at regular
intervals during transfers. Good sampling helps to ensure
accurate accounting and accurate accounting provides a back
up if the ^ books don't balance.'
f . No gold should leave the goldroom without being recorded in
the ""gold movement' record book; the entry duly witnessed.
No gold products should be stored outside of the goldroom,
g. If returning to the goldroom after hours, make sure that
the shift foreman is aware of your presence, and preferably
note the reason for and time of your visit in the shift log
book.
h. Do not allow any unauthorised person to enter the goldroom.
All visitors should be entered in the visitors book.
i. Do not leave your goldroom keys lying around - or allow
others to use them. (Ninety nine percent of the people
around this plant would be quite capable of copying them. >
j. When despatching bullion of a Wednesday morning, keep the
goldroom doors locked until such time as the bars have been
signed out and all of the necessary paperwork associated
with their despatch, completed. Only then should the
loaded bullion boxes be taken out to the vehicle and the
security guard should be standing by the vehicle when this
JO u
is done.
k. Maintain radio contact with the gold movement vehicle until
the gold plane has taken off.
-57-
10.3 Safety
a. Reagents and Fluxes
This gold plant uses an assortment of reagents and fluxes
most of which possess same or all of the following
characteristics: -
<i> Highly corrosive.
(ii) Highly poisonous
<iii) Inflamable - if combined with some other
reagents or materials.
<iv) Explosive - when combined with some other
reagents or substances.
All employees should read the information sheets at the end
of this section relating to individual reagents and fluxes.
They should take particular note of the appropriate first aid
attention necessary in the case of adverse exposure.
b. Handling
Prevention is bettere than cure! Wear appropriate safety
gear when handling liquid reagents or fluxes. When handling
liquid reagents, wear rubber gloves and a full face mask with
appropriate cartridge filter. Far mast goldroom reagents a
filter suitable for organic vapours is appropriate but when
handling cyanide a cartridge specifically for use in cyanide
contaminated areas must be used.
When mixing fluxes, rubber gloves, safety glasses and
disposable face mask must be used. Even the most harmless of
the fluxes, silica flour, (not included in the information
sheets as it does not possess any of the characteristics
detailed in section 9.3a> can have serious long term
respiratory effects if inhaled.
Extreme care should be taken when drying concentrate or cake.
The fumes given off can at times be quite toxic or Irritating
if inhaled. When in doubt wear a mask! Or hold your breath.
c. General Safety
(i) Normal safety rules apply within the goldroom surrounds.
Safety boots must be worn at all times and when working
outside of the actual goldroom, a safety helmet must be
worn. Safety glasses must be worn in the proximity of the
acid and elution columns when they are operating.
(ii) Good housekeeping is essential at all times. Do not leave
-58-
things lying on the floor and clean up all spills
immediately after they occur.
(iii) When working on any piece of equipment make sure that it
has been appropriately isolated and tagged out at the main
control panel
(iv) If inspecting "in column screens' or changing heat
exchanger plates, ensure that all necessary manual valves
are closed and that any associated pumps are isolated and
tagged out,
(v) When working near the furnace on smelting days, full
protective clothing must be worn.
<vi> Always wear gloves when handling slag. Even when cold it
can inflict harm as it may be very sharp.
i
I
I
I
-59-
10. 4 Reagents - Their Effects
on
Requiremnets. Handling and Disposal.
Human Beings. First Aid
BORAX
DESCRIPTION
HAZARDS
— 7
White odourless powder.
Acute poison
EFFECT
PRODUCT IN EYE
Irritant
PRODUCT ON SKIN
PRODUCT INHALED
PRODUCT INGESTED Toxic
FIRST AID
Irrigate immediately with
copious water for 10
minutes. Seek urgent
medical attention.
Vash off with plenty of
water, removing affected
clothing and washing
underlying skin. Clean
clothing before re-use.
Remove from exposure,
warm and at rest. If
distressed respirator! ly,
seek urgent medical
attention.
Vash mouth out with water
and give an emetic. Seek
urgent medical attention.
HANDLING
DISPOSAL
Wear fully protective clothing
full-face mask with respirator.
Sweep up,
gloves
and
-60-
BORIC ACID
DESCRIPTION
HAZARDS
Vliite crystals or powder.
Toxic by absorption and ingestion. Affects
central nervous system
EFFECT
PRODUCT Iff EVP Irritant
PRODUCT ON SKIN
Toxic by absorp-
tion if in large
quantities,
PRODUCT INHALED
PRODUCT INGESTKD Toxic, nausea,
vomiting, diarr-
hoea , shock.
FIRST AID
Irrigate immediately for
10 minutes with copious
water. Seek medical
attention.
Wash off with plenty of
water, removing affected
clothing and washing
underlying skin. Seek
medical attention.
Remove from exposure. If
effects persist seek
medical attention.
Vash mouth out with water
and give water to drink.
Seek urgent medical
attent ion.
i
HANDLING
STORAGE
DISPOSAL
Wear full protective clothing,
gloves and safety glasses,
unnecessary contact.
Store away from strong alkalis.
Vash away with plenty of water.
mask, rubber
Avoid all
i
CAUSTIC SODA
DESCRIPTION White lumps or sticks
HAZARDS
Corrosive on all body tissues,
water or steam to produce heat
Reacts with
EFFECTS
FIRST AID
PRODUCT IK EYE
Severe Burns
PRODUCT ON SKIN Severe Burns
PRODUCT INHALED
Damage to upper
respiratory tract
and lung tissue.
PRODUCT INGESTED Severe burns, Pos-
sible ulceration.
Irrigate immediately with
copious water for 10
minutes. Seek urgent
medical attention.
Wash off with plenty of
water, removing affected
c 1 ot h i ng and wash i ng
underlying skin. Clean
clothing before re-use .
Seek urgent medical
attention.
Remove from exposure. Keep
warm and at rest. Seek
urgent medical attention.
DO NOT
induce
vomiting.
Wash mouth out with water.
Seek urgent medical
attention.
HANDLING
DISPOSAL
Wear fully protective clothing including gloves
, safety glasses and boots. Avoid breathing the
vapour .
Flood with copious water.
-62-
HYDROCHLQR I C ACID
DESCRIPTION
HAZARDS
FIRE
EXPLOSION
Colourless or pale yellow fuming liquid with
pungent acidic odour.
Corrosive liquid and vapour
Non-Flammable. But gives off toxic fumes when
heated. Tanks to be kept cool. Safety glasses
and breathing apparatus to be worn.
A contact with some metals will cause highly
flammable hydrogen gas to be given off.
PRODUCT IN EYE
PRODUCT ON SKIN
PRODUCT INHALED
PRODUCT INGESTED
EFFECTS
FIRST AID
LIQUID :
Severe Burns
VAPOUR :
Burns at high con-
centration. Irrit-
ant at low concen-
trations .
LIQUID :
Burns
VAPOUR :
Irritation
High concentrat-
ions produce con-
siderable respir-
atory distress and
painful coughing.
Possible lung dam-
age. Not voluntar-
ily tolerable.
Irrigate immediately with
copious water for 10
minutes. Seek urgent
medical attention.
Wash off immediately with
plenty of water, removing
affected clothing and
washing underlying skin.
Clean affected clothing.
Remove from exposure, keep
warm and at rest. If
distressed respiratorily ,
give oxygen and seek urgent
medical attention.
Systemic
not known.
effects
Seek urgent medical attent-
ion. DO NOT induce vomit-
ing.
HANDLING
STORAGE
DISPOSAL
Vear fully protective clothing, full ;
with respirator and rubber gloves.
Do not store
metals.
in containers made of
Avoid contact with liquid. Estinguish source of
ignition. Flood with water bearing in mind that
the first run off will be highly corrosive. In-
form authorities if a major spillage occurs.
-63-
L I ME
DESCRIPTION
HAZARDS
White amorphous powder.
Reacts vigorously with water giving off consid-
erable heat. Similar reaction with steam, acids
or acid fumes.
EFFECT
FIRST AID
PRODUCT IN EYE Severe Burns
PRODUCT ON SKIN Severe irritant.
PRODUCT INHALED
Irritant to muc-
ous membranes
and upper res-
piratory tract.
PRODUCT INGESTED Toxic affects.
Irrigate immediately with
copious water for 10
minutes and seek urgent
medical attention.
Vash with plenty of soap
and water . Remove affected
clothing and clean before
re-use.
Remove from exposure. Keep
warm and at rest. If
distressed respiratorily ,
seek urgent medical
attention.
Vash mouth out with water
and give plenty of water to
drink. Seek urgent medical
attention.
HANDLING
DISPOSAL
Wear f ul 1 protective
and safety glasses.
Flush away with water.
gloves
-64-
KJ1ICACID
5ISCRIPTI0K
HAZARDS
■
FIRE
Colou r le ss or yellowish fumlng
-acts wifh wate^o f ££Wtio..
Non-Combustible.
EFFECTS
FIRST ATP
PRODUCT Iff EYF o
XJt nx ± Severe Burns
^ODUOLOILSKIN Burns
?5B82£T — INHALED Irritant - will
cause pulmonary
damage .
PRODUCT WSSmSZ Severe internal
irritation.
Irrigate immediately with
se^kin* ^ WatSr Whlle
attention. UrSSnt "* d± °**
Vash with plenty of warm
re ^ving affected
clothing and cleaning
before re-use. Seek urgent
medical attention. S
warT* ex P osu ^. keep
warm and at rest. Seek
urgent medical attention.
with ^waLr ^ th -° UShly
wa^er. and seek
urgent medical attenti,
on.
HANDL I NG
DISPOSAL
SSr^n^SiS "*^! powd — —bid..,
all combustible^ Z ^^nic acid and
oxidisable materials ° ther ™*«ily
Spread soda ash, if avail* hi-
and m op up cautiously with w!;= ° V S r the are *
and continue diluting rtti Z f " EUD to wast «
8 wlth running water.
-65-
SODA ASH
DESCRIPTION
HAZARDS
White odourless crystalline powder
Poisonous if taken internally.
EFFECT
PRODUCT IN EYE Irritant
PRODUCT ON SKIN Blisters?
PRODUCT INHALED Irritant
PRODUCT INGESTED Poisonous
FIRST AID
Irrigate immediately with
copious water for 10
minutes.
Wash off with plenty of
water, removing affected
clothing and cleaning
before re-use .
Remove from exposure, keep
warm and at rest. If
distressed respirator i ly,
seek urgent medical
attention.
Wash mouth out with water,
give water to drink. Seek
urgent medical attention.
HANDL I NG Avoid dust
DISPOSAL
Mop up with water and run to waste, diluting
with water.
-66-
SQDIUM CYAN IDE
DESCRIPTION
HAZARDS
FIRE -
EXPLOSION
White crystalline powder
Emits toxic and flammable vapour on contact
with acid, acid fumes, water or steam.
Extinguish with dry powder, alcohol foam or
carbon dioxide.
Explosive when decomposing to hydrocyanic acid.
Reacts violently with nitrite and nitrate.
EFFECTS
PRODUCT IN EYE
Corrosive
PRODUCT ON SKIN
Irritant and may
cause secondary
infection.
PRODUCT INHALED
Poisonous - may
cause loss of
appetite, head-
ache, nausea,
dizziness and
upper tract irr-
itation.
PRODUCT INGESTED Highly poisonous
FIRST AID
Irrigate immediately with
copious water for 10
minutes. Seek urgent medic-
al attention.
Wash with plenty of water,
removing affected clothing
and washing underlying
skin. Clean clothing before
re-use .
Remove from exposure. Keep
warm and at rest . Seek
urgent medical attention.
Induce vomiting and seek
urgent medical attention.
HANDLING
DISPOSAL
Wear rubber
respirator .
No
aprons,
smoking,
rubber gloves and
Sweep up. DO NOT flush with water.
-67-
SODIUM NITRATE
DESCRIPTION
HAZARDS
Colourless, odourless crystals with a slightly
bitter taste .
Explosive when mixed with finely divided
combustible materials, cyanides, sodium
hypophosphite . Highly toxic when ingested.
EFFECT
FIRST AID
PRODUCT IN EYE Irritant
PRODUCT ON SKIN Irritant
PRODUCT INGESTED
Gastro-enterit is
.abdominal pains
, vomiting, musc-
ular weakness,
irregular pulse,
convulsions and
col lapse .
Irrigate immediately for 10
minutes with copious water.
Seek medical attention.
Wash off with plenty of
water, removing affected
clothing and washing
thoroughly before re-use .
If effects persist seek
medical attention.
Wash mouth out with water
and give an emetic. Seek
urgent medical attention.
HANDLING
STORAGE
DISPOSAL
FIRE FIGHTING
Wear full safety clothing, mask, rubber gloves
and safety glasses. Avoid dust inhalation,
Store in a dry place away from strong reducing
agents and organics.
Sweep up and wash spillage area thoroughly with
water.
Ignites on friction when mixed with organic
material. Use water spray extinguisher and
W6 3 r
-68-
REFBRBNCBS
Clyde Carruthers Handbook
"Operation, Maintenance and Installation Instructions for Clyde
Vilfley Concentrating Table No, 12, Serial Ho. 2143, October 85."
Comsteel Vickers Limited (Fine Hinerals Engineering Division)
"Installation and Operations Manual for Vickers FG Spirals and
Vickers Static Distributor, November 85."
Kleenheat Gas Handbook
"Operating Instructions for Vest farmers Kleenheat Gas Pty. Ltd.
Gold Melting Furnace - Tilting Type."
Mount Percy Mining Services Pty. Ltd.
"Operations Manual."
Western Australian Mining and Petroleum Research Institute Report
No . 2 .
"Carbon-in-Pulp Gold Processing Technology - Project No. 10."
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